Tripwire Interactive announces that Killing Floor has sold more than 1 million copies on the PC, celebrating the milestone with a sale on Steam where the action game and all its DLC can be had at an 85% discount. They also offer some sales stats for the game:

1.1 MILLION copies of Killing Floor sold on PC in 2 and a half years

Nearly 2 million Killing Floor DLC packs sold

45 MILLION hours of Killing Floor played to date

440 MILLION Zeds have been dispatched in Achievements alone - including more than a quarter-million Christmas Santa

I like the idea, but for a 2010 release, I expected a bit more, it's like a cross of L4D and MW zombies, it's not as polished as it could be, and in desperate need of a model upgrade, uninstalled without prejudice